Various types of electronic locks and keys are well known in the art. Rode in U.S. Pat. No. 3,944,976 has shown a security system in which a random bit pattern can be stored and interchanged between an electronic lock and a mating key by either conductive or radiative connections. Kip et al. in U.S. Pat. No. 4,196,418 and Walton in U.S. Pat. No. 4,388,524 have also shown electronic locks and keys that interact via radiative connections. It is desirable to use such an electronic lock and key to provide a complete facility security system that is flexible, has fast response, and is protected from failures of either the AC power or of modules within the system.